Nonwoven abrasive products are well known, for example, as disclosed in Hoover et al., U.S. Pat. No. 2,958,593. Such products are characterized by having abrasive particles dispersed throughout, and adhered in, a three-dimensional nonwoven fibrous web. Barnett et al., U.S. Pat. No. 4,609,380, discloses an abrasive wheel formed by adhering together layers of a nonwoven abrasive material of the type disclosed in Hoover et al., which is improved by the inclusion of a binder system comprising a blend of a tough adherent binder and a smear-reducing compatible polymer.
The refinement of glass and ceramic surfaces with abrasive materials is also well known. The abrasive material may be incorporated into an article, e.g., adhered to a backing or adhered within a three-dimensional matrix, or it may be fed as a slurry to the interface of a finishing tool and the workpiece.
Examples wherein the abrasive materials are adhered to a backing to form an abrasive article are disclosed in Schroeder, U.S. Pat. No. 2,865,725, Stoppacher, U.S. Pat. No. 3,959,935, and Anthon, U.S. Pat. No. 3,230,672. Schroeder adheres finely ground cerium oxide powder to a flexible sheet, preferably cotton fabric, to provide a polishing article. Stoppacher adheres an abrasive such as silicon carbide or garnet to a pliable sheet of paper, polymer, cloth, or nonwoven textile fabric to provide a lens grinding pad. Anthon discloses cushion mounting oriented particles of an abrasive material on a mesh fabric backing. The abrasive particles are predominantly oriented so as to present their plane faces or facets, and not their sharp edges or points, toward the work surface in a common plane parallel to the support. The oriented abrasive particles are adhered to the backing with an adhesive such as latex which is pliable, yieldable, or resilient when set. The cushion mounted abrasive particles can slightly rock or tilt, or recede, to accommodate themselves to the contour of the work surface thereby reducing surface abrasion and scratching.
Examples where the abrasive is adhered in a three-dimensional matrix are found in Hall, U.S. Pat. No. 3,597,887, and Hartfelt et al., U.S. Pat. No. 4,138,228. Hall discloses an abrasive wheel comprised of individual flexible elements secured together, wherein each element comprises an abrasive substance adhered in a matrix of synthetic resinous elastomeric foam permanently bonded in and to a fibrous mesh. Hartfelt et al. discloses adhering particles of abrasive, of average size less than 10 microns, from the rare earth oxide or metal oxide classes of compounds in a microporous polymer matrix coated on a backing. The microporous polymer must be a hydrophilic water-absorbing polymer, or a polymer which forms only a weak bond with the abrasive particles, so that a controlled release of the abrasive particles from the matrix is obtained during use.
The use of abrasive material in a slurry to polish glass is also well known in the art. Such abrasive materials include silicon carbide, vitreous silica, garnet, metal oxides, rare earth oxides, and mixtures of known abrasives with rare earth oxides. Harman et al., U.S. Pat. No. 2,744,001, for example, disclose the addition of rare earth oxides to vitreous silica, each having a particle size of 20 microns or less, to produce a slurry-type polishing mixture that is superior to either of the component materials used alone.
While a considerable need exists to provide a finishing article for use on glass and ceramics which rapidly achieves a desired polished surface, comparable to the result achieved with slurry polishing, as far as is known no such article exists.